New Drug and Possible New Toxicity - Squamous Cell Carcinoma Following Imatinib in Patients with Gastrointestinal Stromal Tumors

Background: Molecularly targeted therapy has revolutionized the treatment of advanced gastrointestinal stromal tumors (GISTs). Specifically, the consistent dependence of GISTs on proto-oncogene c-KIT signaling led to the development and successful implementation of imatinib, a small-molecule c-KIT inhibitor. Imatinib induces, rapid and sustained clinical benefit by blocking the signaling via c-KIT. The most frequently reported adverse reactions (>30%) include edema, nausea, vomiting, muscle cramps, musculoskeletal pain, diarrhea, rash, fatigue and abdominal pain.

Case series: Herein, we report a case series of cutaneous squamous cell carcinoma (SCC) occurring secondary to imatinib in two patients treated for GISTs. Both patients were successfully managed with surgical resection of SCC and the discontinuation of the drug. Furthermore, we undertook a comprehensive literature review on this association. Few cases of cutaneous SCC secondary to imatinib therapy were reported in patients with chronic myeloid leukemia. However, there was no clinical evidence on causation of imatinib-associated SCC in patients with GIST.

Conclusion: To our knowledge, the present report is the first to describe imatinib-related SCC in patients undergoing treatment for GISTs. This implicates that safety and long-term tolerability of imatinib in patients with GISTs warrant rigorous testing and close monitoring.